1. Field of the Invention
This invention relates to integrated circuit structures and to processes for fabricating them. In particular, the invention relates to a semiconductor structure in which a bipolar transistor and a Schottky diode are merged.
2. Description of the Prior Art
In the design and manufacture of integrated circuits, Schottky diodes and transistors are often connected as part of a larger circuit, for example, a logic gate. In the prior art these interconnections have been formed using conventional techniques such as fabricating the Schottky diode near the transistor to which it is to be connected, and then interconnecting the two components with a metal line. In some prior art techniques the Schottky diode has been formed on top of the silicon substrate in which one or more transistors are formed.
Furthermore, the Schottky clamped transistors of the prior art typically used heavily doped regions of boron, fabricated using conventional bipolar processing, for the base contact. The Schottky diode was then usually formed on additional epitaxial area adjacent to the base of the transistor. This structure resulted in an active transistor with an additional diode formed by the heavily doped base region, and a Schottky diode, both in parallel with the base-collector contacts of the transistor. The additional PN junction diode formed by the extrinsic base and epitaxial layer was a significant limitation on the switching speed of the transistor.